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| United States Patent |
5,270,110
|
|
Murakami
, et al.
|
December 14, 1993
|
Film-forming organopolysiloxane composition
Abstract
A film-forming organopolysiloxane composition is disclosed which imparts an
excellent releaseability and lubricity to the surface of various types of
rubber materials. The composition comprises a solvent dispersion of
(a) 50 to 90 weight percent of a block organopolysiloxane copolymer;
(b) 2 to 50 weight percent of a compound selected from the group consisting
of an organosilane or a partial hydrolyzate thereof;
(c) 4 to 40 weight percent of a mixture an epoxy group-containing
organoalkoxysilane and an alkenyl group-containing organoacetoxysilane in
a weight ratio of 1:9 to 9:1 or a condensation-reaction product thereof;
(d) 0.1 to 10 weight percent of an hydroxy or alkoxy terminated
diorganopolysiloxane; and
(f) 0.1 to 10 weight percent of a condensation-reaction catalyst.
| Inventors:
|
Murakami; Ichiro (Ichihara, JP);
Motomura; Hideyuki (Ichihara, JP)
|
| Assignee:
|
Dow Corning Toray Silicon Co., Ltd. (Tokyo, JP)
|
| Appl. No.:
|
051419 |
| Filed:
|
April 23, 1993 |
Foreign Application Priority Data
| Current U.S. Class: |
428/355R; 428/447 |
| Intern'l Class: |
B32B 007/12 |
| Field of Search: |
428/447,355
|
References Cited
U.S. Patent Documents
| 4115356 | Sep., 1978 | Hilliard | 528/18.
|
| 4122127 | Oct., 1978 | Mikami et al. | 528/18.
|
| 4431472 | Feb., 1984 | Hohl et al. | 528/901.
|
| 4595610 | Jun., 1986 | Fey et al. | 528/21.
|
| 4673750 | Jun., 1987 | Beers et al. | 528/18.
|
| 4973623 | Nov., 1990 | Haugsby et al. | 528/34.
|
| 4996112 | Feb., 1991 | Perrin et al. | 528/901.
|
| 5013781 | May., 1991 | Koshii et al. | 528/34.
|
| Foreign Patent Documents |
| 1-198840 | Jul., 1989 | JP.
| |
Primary Examiner: Marquis; Melvyn I.
Assistant Examiner: Dean; Karen A.
Attorney, Agent or Firm: Gearhart; Richard I.
Parent Case Text
"This is a divisional of copending application(s) Ser. No. 07/728,452 filed
on 7/11/91" now 5,246,995.
Claims
That which is claimed is:
1. A rubber substrate coated with a film-forming organopolysiloxane
composition comprising an organic solvent dispersion of
(a) 50 to 90 weight percent of a block organopolysiloxane copolymer
composed of
(i) 10 to 80 weight percent of an organopolysiloxane resin composed of
R.sub.x SiO.sub.(4-x)/2
units, wherein R is a monovalent hydrocarbon group and x has an average
value of 1.0 to 1.3,
(ii) 2 to 30 weight percent of end-blocking siloxane unit composed of
R.sup.1.sub.y R.sup.2 SiO.sub.(3-y)/2
units, wherein R.sup.1 is a silicon-bonded hydrolyzable group, R.sup.2 is
a monovalent hydrocarbon group and y has an average value of 1.8 to 2.0,
and
(iii) 10 to 80 weight percent of a straight-chain organopolysiloxane
composed of
R.sup.3.sub.2 SiO
units, wherein R.sup.3 is a monovalent hydrocarbon group, at least 80 mole
percent of said R.sup.3 group being methyl;
(b) 2 to 50 weight percent of a compound selected from the group consisting
of an organosilane having the general formula
##STR2##
wherein R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are monovalent hydrocarbon
groups, a is zero, 1, 2, 3 or 4, b is zero, 1, 2, 3 or 4, a+b is 3 or 4, c
is zero or 1 and a+b+c is 4, and a partial hydrolyzate of said
organosilane;
(c) 4 to 40 weight percent of a component selected from the group
consisting of a mixture of an epoxy group-containing organoalkoxysilane
and an alkenyl group-containing organoacetoxysilane in a weight ratio of
1:9 to 9:1 and a condensation-reaction product of said mixture;
(d) 0.1 to 10 weight percent of a diorganopolysiloxane which is terminated
with a group selected from the group consisting of an hydroxyl group and
an alkoxy group; and
(f) 0.1 to 10 weight percent of a condensation-reaction catalyst.
2. The rubber substrate coated with a composition according to claim 1,
further comprising a filler selected from the group consisting of an
organic micropowder and an inorganic micropowder, wherein said filler is
present at a level of up to 10 weight percent based on the 50 to 90 weight
percent of said block copolymer (a).
3. The rubber substrate coated with a composition according to claim 1,
wherein R is selected from the group consisting of methyl and phenyl
radicals.
4. The rubber substrate coated with a composition according to claim 3,
wherein R.sup.2 is a methyl radical and R.sup.1 is selected from the group
consisting of methoxy and ethoxy groups.
5. The rubber substrate coated with a composition according to claim 4,
wherein said diorganopolysiloxane (d) is polydimethylsiloxane.
6. The rubber substrate coated with a composition according to claim 5,
wherein said compound (b) is selected from the group consisting of
methyltris(methyl ethyl ketoxime)silane, vinyltris(methyl ethyl
ketoxime)silane, methylmethoxydi(methyl ethyl ketoxime)silane,
diethoxydi(methyl ethyl ketoxime)silane, methyltrimethoxysilane,
methyltriethoxysilane, vinyltrimethoxysilane, mixtures thereof and partial
hydrolysis-condensates thereof.
7. The rubber substrate coated with a composition according to claim 6,
wherein said epoxy group-containing organoalkoxysilane of said component
(c) is selected from the group consisting of
gamma-glycidoxypropyltrimethoxysilane,
gamma-glycidoxypropyltriethoxysilane and
beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and said alkenyl
group-containing organoacetoxysilane is selected from the group consisting
of vinyltriacetoxysilane and allyltriacetoxysilane.
8. The rubber substrate coated with a composition according to claim 7,
wherein said film-forming organopolysiloxane composition comprises an
organic solvent dispersion of 50 to 90 weight percent of said block
organopolysiloxane copolymer (a), 5 to 40 weight percent of said compound
(b), 5 to 15 weight percent of said component (c), 0.1 to 5 weight percent
of said diorganopolysiloxane (d), 0.3 to 5 weight percent of said
condensation-reaction catalyst (f) and the weight ratio of said epoxy
group-containing organoalkoxysilane to said alkenyl group-containing
organoacetoxysilane is 3:7 to 7:3.
9. The rubber substrate coated with a composition according to claim 6,
further comprising a filler selected from the group consisting of an
organic micropowder and an inorganic micropowder, wherein said filler is
present at a level of up to 10 weight percent based on the 50 to 90 weight
percent of said block copolymer (a).
10. The rubber substrate coated with a composition according to claim 7,
further comprising a filler selected from the group consisting of an
organic micropowder and an inorganic micropowder, wherein said filler is
present at a level of up to 10 weight percent based on the 50 to 90 weight
percent of said block copolymer (a).
Description
The present invention relates to a film-forming organopolysiloxane
composition which imparts an excellent releaseability and lubricity to the
surface of various types of rubber materials.
BACKGROUND OF THE INVENTION
The following techniques are already known for imparting release and
lubrication properties to the surfaces of various types of rubber
materials:
(a) coating said surface with a strongly releasing, highly lubricating
silicone oil or fluorine-type oil;
(b) coating and curing a releasing and lubricating silicone resin onto said
surface.
However, the technique of applying a strongly releasing, highly lubricating
oil suffers from the problem of the gradual decline in the effect of the
coated oil due to its loss from the surface with the passage of time. In
addition, with regard to the coating and curing of a releasing and
lubricating silicone resin, the cured resin film thus obtained cannot
follow or track the rubber material's elongation. This results in a
pronounced tendency for cracking to occur on the surface of the rubber
material during the expansion and contraction which accompanies its
flexing. The releaseability and lubricity are then lost, and the external
appearance is compromised at the same time. Thus, rubber materials which
employ this approach cannot tolerate long-term application.
In order to solve these problems arising in the prior art, the present
inventors have already proposed a film-forming organopolysiloxane
composition made from a special organopolysiloxane composition (refer to
Japanese Patent Application Number 01-198840 [198,840/89]). However, while
this composition evidences good adherence to silicone rubbers and
fluororubbers, its adherence for other organic rubbers is somewhat poor,
and it does not always provide a satisfactory performance when such other
organic rubbers are deployed in service accompanied by such actions as
friction or flexing.
SUMMARY OF THE INVENTION
The present inventors carried out extensive research directed at solving
the problems listed above. As a result, they discovered that the
aforementioned problems, and particularly the problem of adhesion to
organic rubbers other than silicone rubbers and fluororubbers, can be
substantially solved by coating and curing an organopolysiloxane
composition containing special organosilanes onto the surface of the
rubber material. The present invention was achieved based on this
discovery.
In other words, the present invention takes as its object the introduction
of a film-forming organopolysiloxane composition which can form a
self-bonding, rubbery elastic cured film that strongly adheres to various
types of rubber materials, and particularly to organic rubbers other than
silicone rubbers and fluororubbers, while imparting an excellent
releaseability and lubricity to the surface of the coated rubber.
The present invention therefore relates to a film-forming
organopolysiloxane composition for imparting releaseability and lubricity
to the surface of various types of rubber materials, which
characteristically consists of
(a) 50 to 90 weight % of a block organopolysiloxane copolymer composed of
(i) 10 to 80 weight % organopolysiloxane resin composed of
R.sub.x SiO.sub.(4-x)/2
units, wherein R is a monovalent hydrocarbon group and x has an average
value of 1.0 to 1.3.
(ii) 2 to 30 weight % end-blocking siloxane units composed of
R.sup.1.sub.y SiR.sup.2 O.sub.(3-y)/2
units, wherein R.sup.1 is a silicon-bonded hydrolyzable functional group,
R.sup.2 is a monovalent hydrocarbon group, and y has an average value of
1.8 to 2.0, and
(iii) 10 to 80 weight % straight-chain organopolysiloxane composed of
R.sup.3.sub.2 SiO
units, wherein R.sup.3 is a monovalent hydrocarbon group, of which at least
80 mole % is methyl;
(b) 2 to 50 weight % of an organosilane having the general formula
##STR1##
wherein R.sup.4, R.sup.5, R.sup.6, and R.sup.7 are monovalent hydrocarbon
groups, a is zero, 1, 2, 3, or 4, b is zero, 1, 2, 3, or 4, a+b is 3 or 4,
c is zero or 1, and a+b+c+d is 4 or the partial hydrolyzate thereof;
(c) 4 to 40 weight % of an epoxy group-containing organoalkoxysilane and an
alkenyl group-containing organoacetoxysilane, or their
condensation-reaction product;
(d) 0.1 to 10 weight % of an diorganopolysiloxane having an hydroxyl or an
alkoxy group at the molecular terminal;
(e) zero to 10 weight % inorganic or organic micropowder;
(f) 0.1 to 10 weight % condensation-reaction catalyst; and
(g) an arbitrary quantity of organic solvent.
DETAILED DESCRIPTION OF THE INVENTION
To explain the preceding in greater detail, the principal or main component
of the present invention is the block organopolysiloxane copolymer
comprising the component (a) used by the present invention. This component
comprises a block organopolysiloxane copolymer composed of
(i) 10 to 80 weight % organopolysiloxane resin composed of
R.sub.X SiO.sub.(4-x)/2
units, wherein R is a monovalent hydrocarbon group, for example, an alkyl
group such as methyl, ethyl, or propul, etc., or an aryl group such as
phenyl, etc.; and x has an averge value of 1.0 to 1.3,
(ii) 2 to 30 weight % end-blocking siloxane unit composed of
R.sup.1.sub.y SiR.sup.2 O.sub.(3-y)//2
units, wherein R.sup.1 is hydrolyzable functional group which is
exemplified by alkoxy groups such as methoxy, ethoxy, propoxy, etc., by
oxime groups such as methyl ethyl ketoxime, etc., and by the acetoxy
group; R.sup.2 is monovalent hydrocarbon group, for example, an alkyl
group such as methyl, ethyl, or propylo, etc., or an aryl group such as
phenyl, etc.; and y has an average value of 1.8 to 2.0, and
(iii) 10 to 80 weight % straight-chain organopolysiloxane composed of
R.sup.3.sub.2 SiO
`units, wherein R.sup.3 is a monovalent hydrocarbon group, for example, an
alkyl group such as methyl, ethyl, or propyl, etc., or an aryl group such
as phenyl, etc., of which at least 80 mole % is methyl.
This block organopolysiloxane copolymer is exemplified by block
organopolysiloxane copolymers obtained by the condensation reaction of a
dimethylpolysiloxane carrying silanol groups or alkoxy groups at the
molecular chain terminals, with the hydrolysis condensate of a
phenyltrialkoxysilane such as C.sub.6 H.sub.5 Si(OCH.sub.3).sub.3, C.sub.6
H.sub.5 Si(OC.sub.2 H.sub.5).sub.3. It may also be exemplified by block
organopolysiloxane copolymers obtained by the condensation reaction of a
dimethylpolysiloxane carrying silanol groups or alkoxy groups at the
molecular chain terminals, with the hydrolysis condensate of a
methyltrialkoxysilane such as CH.sub.3 Si(OCH.sub.3).sub.3 or CH.sub.3
Si(OC.sub.2 H.sub.5).sub.3.
With regard to the preparation of these organopolysiloxanes, the
hydrolysis/condensation reaction of the aforementioned organosilanes is
preferably gradually developed in a nonpolar solvent (for example,
toluene, xylene, etc.) by the addition of the required quantity of water.
Hydrochloric acid or the metal salt of octylic acid, naphthenic acid,
etc., should be used as catalyst for the production of the block copolymer
by the condensation reaction. The silicon-bonded hydrolyzable functional
groups may be introduced through a partial hydrolysis of the
aforementioned alkoxysilane in order to leave residual alkoxy groups or by
running an end-blocking reaction during the condensation reaction by the
addition of hydrolyzable silane.
The organosilane comprising the component (b) used by the present invention
is a crosslinker for the organopolysiloxane comprising component (a), and
it is the essential component for inducing adhesion between the
composition of the present invention and various types of rubber
materials. The groups R.sup.4, R.sup.5, R.sup.6, and R.sup.7 in the
formula given above comprise monovalent hydrocarbon groups as exemplified
by alkyl groups such as methyl, ethyl and propyl, and by alkenyl groups
such as vinyl and allyl. The organosilane under consideration is
exemplified by oxime group-containing organosilanes such as
methyltris(methyl ethyl ketoxime)silane and vinyltris(methyl ethyl
ketoxime)silane; organosilanes which contain both the oxime group and
alkoxy group, such as methylmethoxydi(methyl ethyl ketoxime)silane and
diethoxydi(methyl ethyl ketoxime)silane; alkoxy group-containing
organosilanes such as methyltrimethoxysilane, methyltriethoxysilane and
vinyltrimethoxysilane; as well as by mixtures of the preceding. This
crosslinking component may also take the form of the partial
hydrolysis-condensate obtained by a reaction in which the necessary
quantity of water is added to an organosilane, as listed above.
The component (b) under consideration is added within the range of about 2
to 50 weight %, and preferably within the range of 5 to 40 weight %,
relative to 50 to 90 weight % of component (a). The composition of the
present invention will be inadequately crosslinked at an addition below
about 2 weight %. On the other hand, an addition in excess of about 50
weight % causes the cured film to be hard and brittle, and it can then no
longer track the rubber material's elongation.
The component (c) used by the present invention comprises an
epoxy-containing organoalkoxysilane plus an alkenyl-containing
organoacetoxysilane, or the condensation-reaction product therefrom. This
is the critical component for improving adherence by the present
invention's composition to organic rubbers. The addition of either of
these silanes by itself will not lead to the development of an acceptable
effect; rather, it is essential that they both be present in the
composition simultaneously. This component should be added at about 4 to
40 weight %, and preferably at 5 to 15 weight %, relative to 50 to 90
weight % of component (a). In addition, the weight ratio between the
epoxy-containing organoalkoxysilane and the alkenyl-containing
organoacetoxysilane should fall within the range of about 1:9 to 9:1, but
preferably falls within the range of 3:7 to 7:3.
The epoxy-containing organoalkoxysilane under consideration is exemplified
by gamma-glycidoxypropyltrimethoxysilane,
gamma-glycidoxypropyltriethoxysilane and
beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The alkenyl-containing
organoacetoxysilane is exemplified by vinyltriacetoxysilane and
allyltriacetoxysilane. Component (c) may take the form of a mixture of
epoxy-containing organoalkoxysilane and alkenyl-containing
organoacetoxysilane. but it may also take the form of the product obtained
from the preliminary reaction of these two compounds. This preliminary
reaction product can be readily obtained, for example, by heating the
mixture of epoxy-containing organoalkoxysilane and alkenyl-containing
organoacetoxysilane at a temperature above the ambient temperature.
The diorganopolysiloxane comprising the component (d) employed by the
present invention is the component which functions to endow the
composition of the present invention with release and lubrication
properties. In order for this diorganopolysiloxane to react with component
(a) and/or component (b), it must carry a hydroxyl group or alkoxy group
(e.g., methoxy, ethoxy, propoxy, etc.) at the molecular terminal. The main
chain of this diorganopolysiloxane will generally consist of
polydimethylsiloxane, but a portion of these methyl groups may be replaced
by alkyl groups such as ethyl, propyl, etc.; by aromatic hydrocarbon
groups such as phenyl, styryl, etc.; or by substituents which carry
reactive functional groups such as the epoxy group or amino group.
This diorganopolysiloxane is exemplified by
dimethylhydroxysiloxy-terminated dimethylpolysiloxanes,
dimethylhydroxysiloxy-terminated dimethylsiloxane-methylphenylsiloxane
copolymers, dimethylpolysiloxanes blocked at one molecular chain terminal
by the dimethylhydroxysiloxy group and blocked at the other molecular
chain terminal by the trimethylsiloxy group,
dimethylmethoxysiloxy-terminated dimethylpolysiloxanes, and
dimethylmethoxysiloxy-terminated dimethylsiloxane-methylphenylsiloxane
copolymers.
The component (d) under consideration should be added at about 0.1 to 10
weight %, and preferably at 0.1 to 5 weight %, per 50 to 90 weight % of
component (a).
The optional inorganic or organic micropowder comprising the component (e)
used by the present invention functions to provide a further increase in
the release and lubrication properties of the composition according to the
present invention, and this component is added as necessary when higher
levels of performance are required. By imparting roughness to the surface
of the resulting cured film, the inorganic or organic micropowder reduces
the area of contact with any impinging body and thus provides a further
improvement in the release and lubrication properties. No specific
restriction applies to the particle diameter of the micropowder as long as
roughness can be imparted to the cured film, but particle diameters below
5 micrometers are typically used. The material comprising this component
should not dissolve or swell in the organic solvent used in the
composition according to the present invention, described infra. Nor
should the particles aggregate during long-term storage. This component
(e) is exemplified by such inorganic micropowders as talc, silica,
bentonite, and the like, and by such organic micropowders as polyethylene
micropowder, fluororesin micropowder and silicone resin micropowder.
The component (e) under consideration should be added at a level of up to
about 10 weight %, and preferably at 0.5 to 5 weight %, relative to 50 to
90 weight % of component (a).
The condensation-reaction catalyst comprising the component (f) used by the
present invention functions to promote or accelerate curing by the
composition of the present invention. The condensation-reaction catalyst
under consideration is exemplified by organometallic catalysts such as
dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate,
dibutyltin dioctoate, zinc naphthenate, cobalt naphthenate, tin octylate,
cobalt octylate, zirconium naphthenate, zirconium octylate and tetrabutyl
orthotitanate, and by amine catalysts (excluding organosilicon compounds)
such as diethanolamine, triethanolamine, and the like.
This component should be added at about 0.1 to 10 weight %, and preferably
at 0.3 to 5 weight %, relative to 50 to 90 weight % of component (a).
The organic solvent comprising the component (g) employed by the present
invention functions to dissolve or disperse the preceding components (a)
through (f) and thus functions to facilitate and support the uniform
coating or application of the present invention's composition on the
surface of the rubber material. This organic solvent is exemplified by
aromatic hydrocarbons such as toluene, xylene and benzene; by aliphatic
hydrocarbons, such as n-hexane, n-heptane, rubber volatiles and
industrial-purpose gasoline; by chlorinated hydrocarbons, such as carbon
tetrachloride, 1,1,1-trichloroethane and perchloroethylene; and by ketone
organic solvents, such as methyl ethyl ketone and methyl isobutyl ketone.
Since this component functions to facilitate uniform application onto the
surface of the rubber material by dissolving or dispersing components (a)
through (f), its quantity of addition is freely selectable. However, it
should generally be used within the range of 40 to 90 weight %, and
preferably within the range of 60 to 80 weight %, of the total
film-forming organopolysiloxane composition of the present invention.
In addition to the components (a) through (g) as described hereinbefore,
the composition according to the present invention may as necessary or
desired, contain colorants, such as dyes, pigments, and the like, as long
as the object of the present invention is not compromised.
When applied to any of various types of rubber materials, the composition
according to the present invention as described above strongly adheres to
the rubber material and endows the surface of same with durable release
and lubrication properties. The composition according to the present
invention may be very simply applied onto the surface of various types of
rubber materials by such coating techniques as spraying, brushing,
immersion, or flow coating followed by standing as such, or by heating
according to the circumstances, in order to bring about simultaneous
curing and drying.
EXAMPLES
The present invention will be explained below in greater detail through
illustrative examples, in which parts=weight parts, the viscosity is the
value at 25 degrees Centigrade, and Ph=phenyl.
In the examples, the adherence was numerically evaluated based on the
number of abrasions necessary to peel or separate the film, the
releaseability was numerically evaluated based on the value of the peeling
resistance, and the lubricity was numerically evaluated based on the
dynamic friction coefficient. These measurement values were obtained by
the following methods.
Peeling resistance
The film-forming organopolysiloxane composition was coated in a prescribed
quantity on the surface of the particular rubber substrate and was then
converted into the cured film by heating for the prescribed time in a
hot-air circulation oven at the prescribed temperature. Using a 2 kg
roller, polyester tape (Polyester Tape 31B from Nitto Denko Kabushiki
Kaisha, Japan, width=4 cm) was pressed onto the surface of the cured film,
and this assembly was allowed to stand as such for 1 hour and was then
used as the measurement specimen.
Using a tensile tester, the tape was subsequently pulled off at a peel rate
of 30 cm/minute and a peel angle of 180 degrees, and the force (g)
required for peeling was measured.
Dynamic friction coefficient
A cured film of the film-forming organopolysiloxane composition was formed
on the surface of the particular rubber substrate by the same method as
for the peeling resistance test. An aluminum plate (5 cm.times.5 cm) was
placed on the resulting surface to serve as the contact element. A load
was placed on top of the plate such that the sum of the weight of the
contact element and the weight of the load was 250 g. The contact element
was then pulled horizontally at a sliding rate of 10 m/minute and the
friction coefficient was calculated from the required pulling force.
EXAMPLE 1
A 60% toluene solution was prepared of a (methoxy+silanol)-containing
polysiloxane resin composed of PhSiO.sub.3/2 units, wherein Ph denotes a
phenyl radical, by carrying out an hydrolysis by adding toluene and 2
moles of water to 1 mole of phenyltrimethoxysilane. To 23 weight parts of
this solution were added 20 weight parts of a silanol-terminated
dimethylpolysiloxane (viscosity=70 centistokes), 10 weight parts
methyltrimethoxysilane, and 50 weight parts toluene for dilution. This was
then condensation polymerized in the presence of a catalytic quantity of
hydrochloric acid, and the produced water and methanol were distilled from
the reaction system together with toluene. Toluene was then added to
adjust the solids content and afford a solution (nonvolatiles=70%,
viscosity=700 centistokes) of a (methoxy+silanol)-containing polysiloxane
made up of phenylpolysiloxane blocks and dimethylpolysiloxane blocks. This
was designated as resin A.
The following were then combined and mixed to afford a film-forming
organopolysiloxane composition: 30 weight parts resin A. 10 weight parts
methyltrimethoxysilane, 3 weight parts
gamma-glycidoxypropyltrimethoxysilane, 3 weight parts
vinyltriacetoxysilane, 0.5 weight parts silanol-terminated
dimethylpolysiloxane (viscosity=14,000 centistokes), 0.2 weight parts
dibutyltin diacetate, and 53.3 weight parts toluene.
This film-forming organopolysiloxane composition was poured onto a
frame-equipped panel, allowed to stand for 1 day at room temperature, and
then heated for 30 minutes at 150 degrees Centigrade to give a 2-mm thick
cured sheet. A tensile elongation of 55% was measured on this cured
product using the measurement method stipulated in JIS K 6301.
This composition was spray coated onto rubber plates (7 cm.times.15
cm.times.0.2 cm) as reported in Table 1, followed by standing for 30
minutes at room temperature and then heating for 30 minutes at 100 degrees
Centigrade to afford the cured film. Bonding to the plate substrate was
evaluated by rubbing with a fingernail, and the obtained results are
reported in Table 1. For comparison, a film-forming organopolysiloxane
composition was prepared by omitting the
gamma-glycidoxypropyltrimethoxysilane and vinyltriacetoxysilane from the
composition of Example 1. Bonding by this composition was evaluated as
above, and these results are also reported in Table 1. In Table 1, a "+"
indicates that the film was not peeled from the substrate when scraped
with a fingernail, while an "x" indicates that the film was peeled.
TABLE 1
______________________________________
present comparison
substrates invention
example
______________________________________
silicone rubber + +
fluororubber + +
urethane rubber + +
butyl rubber + +
natural rubber + X
chloroprene rubber
+ X
Hypalon rubber + +
ethylene/propylene rubber
+ X
nitrile rubber + +
styrene rubber + +
acrylic rubber + X
______________________________________
Among the preceding, the peeling resistance value was measured on the
surface of the coated samples for chloroprene rubber and acrylic rubber,
and these results are reported in Table 2. For comparison, the peeling
resistance value was measured on the corresponding rubber material itself,
and this is reported in Table 2 in the comparison example column.
TABLE 2
______________________________________
substrates present invention
comparison example
______________________________________
peeling resistance
(g/4 cm)
chloroprene rubber
4 120
acrylic rubber
5 530
______________________________________
EXAMPLE 2
A mixture was prepared of 30 weight parts resin A from Example 1, 10 weight
parts methyltris(methyl ethyl ketoxime)silane, 2 weight parts
gamma-glycidoxypropyltrimethoxysilane, 2 weight parts
vinyltriacetoxysilane, 0.5 weight parts silanol-terminated
dimethylpolysiloxane (viscosity=80 centistokes), and 0.3 weight parts
dibutyltin dilaurate. This mixture was diluted to 100 weight parts with a
mixed solvent of n-heptane/methyl ethyl ketone (in a 4/1 weight ratio) to
give a film-forming organopolysiloxane composition. The tensile elongation
of this composition was 81% according to measurement as in Example 1.
Following the procedure given in Example 1, this composition was
flow-coated onto the surface of urethane rubber and ethylene/propylene
rubber (EP rubber) and converted into the cured film, on which the peeling
resistance and dynamic friction coefficient were then measured. The
obtained results are reported in Table 3.
The comparison example column in Table 3 reports the results for
measurement of the peeling resistance and dynamic friction coefficient
directly on the urethane rubber and EP rubber without treatment.
TABLE 3
______________________________________
present comparison
substrates invention
example
______________________________________
peeling resistance
(g/4 cm)
urethane rubber 6 1700
EP rubber 5 320
dynamic friction coefficient
urethane rubber 0.30 0.53
EP rubber 0.32 0.49
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EXAMPLE 3
A film-forming organopolysiloxane composition was prepared by the addition
of 0.5 weight parts bentonite to 100 weight parts of the film-forming
organopolysiloxane composition from Example 2. This composition was
evaluated for its release and lubrication properties as in Example 1, and
the obtained results are reported in Table 4.
TABLE 4
______________________________________
substrates
measurement value
silicone rubber
fluororubber
______________________________________
peeling resistance, g/4 cm
0 0
dynamic friction coefficient
0.24 0.25
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EXAMPLE 4
An adhesion evaluation was conducted as in Example 1, except that in the
present case the 3 weight parts gamma-glycidoxypropyltrimethoxysilane and
3 weight parts vinyltriacetoxysilane used in Example 1 were replaced by a
condensation-reaction product obtained from
gamma-glycidoxypropyltrimethoxysilane and vinyltriacetoxysilane. This
condensation-reaction product was obtained by maintaining the mixture of 1
mole gamma-glycidoxypropyltrimethoxysilane and 1 mole
vinyltriacetoxysilane at 50 degrees Centigrade for 3 days. The obtained
results are reported in Table 5. Another film-forming organopolysiloxane
composition was similarly obtained from the composition of Example 3, but
in this case without the addition of the
gamma-glycidoxypropyltrimethoxysilane+vinyltriacetoxysilane
condensation-reaction product. This composition was subjected to adhesion
testing as above, and the obtained results are reported in the comparison
example column in Table 5.
TABLE 5
______________________________________
present comparison
substrates invention
example
______________________________________
silicone rubber + +
fluororubber + +
urethane rubber + +
butyl rubber + +
natural rubber + X
chloroprene rubber + X
Hypalon rubber + +
ethylene/propylene rubber
+ X
nitrile rubber + +
styrene rubber + +
acrylic rubber + X
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